ホスト直接指定してTLS暗号スイートを確認する方法

ciphersuite.go

package main

import (
	"crypto/tls"
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
)

var (
	flagHost = flag.String("h", "", "hostname to overwrite")
)

func usage() {
	w := flag.CommandLine.Output()
	fmt.Fprintf(w, "usage: %v [options] [url ...]\n", os.Args[0])
	flag.PrintDefaults()
	os.Exit(2)
}

func main() {
	log.SetFlags(0)
	flag.Usage = usage
	flag.Parse()

	if *flagHost != "" {
		t := http.DefaultTransport.(*http.Transport)
		t.TLSClientConfig = &tls.Config{
			ServerName: *flagHost,
		}
	}

	for _, url := range flag.Args() {
		req, err := http.NewRequest("GET", url, nil)
		if err != nil {
			log.Println("can't create a request:", err)
			continue
		}
		if *flagHost != "" {
			req.Host = *flagHost
		}
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			log.Printf("can't fetch from %s: %v", url, err)
			continue
		}
		defer resp.Body.Close()

		fmt.Printf("CipherSuite: %x\n", resp.TLS.CipherSuite)
	}
}